BFS using STL

/*

    Author: Abdullah Al Nayem
    Leading University, Sylhet.
*/

#include <bits/stdc++.h>
#define pb push_back

using namespace std;

vector<bool> v;
vector<vector<int> > g;


void bfs(int startingNode)
{
    queue<int> q;

    q.push(startingNode);
    v[startingNode] = true;

    while (!q.empty()) {

        int x = q.front();
        q.pop();

        cout << x << " ";

        for (int i = g[x][0]; i<g[x].size(); i++) {
            if (!v[i]) {
                q.push(i);
                v[i] = true;
            }
        }
    }
}

int main()
{
    int n, e;
    cin >> n >> e;

    v.assign(n, false);
    g.assign(n, vector<int>());

    int a, b;
    for (int i = 0; i < e; i++) {
        cin >> a >> b;
        g[a].pb(b);
        g[b].pb(a);
    }

    for (int i = 0; i < n; i++) {
        if (!v[i])
            bfs(i);
    }

    return 0;
}